Abstract

Quantitative ^(31)P-NMR and enzymatic analysis of high-energy phosphates were used to characterize an isolated perfused working rabbit heart preparation. In this model, the left side of the heart works against a physiological after-load. Two perfusates, Krebs-Henseleit saline and the perfluorocarbon emulsion FC-43 (perfluorotributylamine), were evaluated in their ability to maintain cardiac function and high-energy phosphate metabolites over a period of 2–3 h. Adenine nucleotides ATP, ADP, phosphocreatine and inorganic phosphate (P_i) were measured by ^(31)P-NMR while monitoring cardiac output and coronary flow. Intracellular pH was determined using the chemical shift of P_i. At the end of each experiment, hearts were freeze clamped and enzymatically assayed for adenine nucleotides, phosphocreatine and P_i. In every experiment, hearts perfused with FC-43 emulsion maintained the same rate of cardiac output as hearts perfused with Krebs-Henseleit saline, but with half the coronary flow rate: FC-43, 22 ± 2.5 (n = 5), Krebs-Henseleit saline 42 ± 2.7 (n = 6) ml/min, P < 0.001. Hearts perfused with FC-43 emulsion showed higher [phosphocreatine] and [ATP] measured by 31P-NMR. For [phosphocreatine]: FC-43 3.2 ± 0.7 (n = 5), Krebs-Henseleit saline 1.7 ± 0.2 (n = 6) μmol/g wet wt., P < 0.01. For [ATP]: FC-43 1.8 ± 0.7 (n = 5), Krebs-Henseleit saline 0.9 ± 0.2 (n = 6) μmol/g wet wt., P < 0.02. [phosphocreatine] and [ATP] determined by ^(31)P-NMR values were identical within experimental error to those values obtained by enzymatic analysis. Comparing [P_i] determined by both methods, 36% of P_i in FC-43-perfused hearts, and only 24% of P_i in Krebs-Henseleit saline-perfused hearts were visible by NMR, indicating that a large proportion of P_i is bound in the intact functioning heart. Similar results were obtained for [ADP]. Using the combined techniques of ^(31)P-NMR and enzymatic assay, we have shown in this model of the isolated working rabbit heart preparation, that FC-43 emulsion maintains significantly better function and high-energy phosphate levels than Krebs-Henseleit saline.

1987 Elsevier.
Received 19 March 1986. Revised manuscript received 6 October 1986.
The authors would like to thank Dr. L. Raijman for her invaluable help and advice, and Cheryl Dix for preparation of the manuscript. This work was supported by the James A. Boswell Foundation, Henry A. Braun Foundation, Max Kade Foundation and the Council for Tobacco Research U.S.A. Inc.